1. Field of the Invention
The present invention relates to an image display unit and a method of manufacturing the image display unit, and more particularly to an image display unit for functioning as a transmission type MEM (Mechanical Electro Modulator) unit and a method of manufacturing the image display unit.
2. Description of the Related Art
There have conventionally been proposed various image display units, and a CRT (cathode ray tube) display device, an LCD (liquid crystal display) device, an LED (light emitting diode) display device and a plasma display device have been used practically for a device using a typical image display unit.
In particular, an LCOS (Liquid Crystal on Si) has been well known as a reflection type image display device and has been used as a reflection type liquid crystal projector or a small-sized image display unit.
In recent years, moreover, an MEM unit has been proposed as the image display unit. The MEM unit is an electromechanical optical modulator for mechanically operating a flexible thin film fabricated on a glass substrate or a plastic film through a micromachining technique by electrostatic force, thereby carrying out optical modulation, and has conventionally been known as a transmission type display unit.
In more detail, for example, a flexible thin film comprising a transparent electrode and a diaphragm is provided on a fixed electrode over a light source through a support section as an optical modulator.
In the optical modulator, a predetermined voltage is applied between both of the electrodes to generate electrostatic force therebetween, thereby flexing the flexible thin film toward the fixed electrode. Correspondingly, the optical characteristic of the unit itself is changed so that a light is transmitted through the optical modulator. On the other hand, a voltage to be applied is set to be zero so that the flexible thin film is elastically returned and the optical modulator shields a light. Thus, the optical modulation is carried out.
FIG. 6 is a sectional view showing the internal structure of such a type as to utilize an interference which is one of the conventional MEM units.
In the MEM unit shown in FIG. 6, two upper and lower transparent electrodes 94 are formed with a spacing on the upper surface of a glass substrate 91 and two upper and lower half mirrors 92 are provided on the lower transparent electrode 94 through two spacers 95. A transparent spacer 93 formed of an insulator is formed in contact with the lower half mirror 92 in a space interposed between the two half mirrors 92 and the two spacers 95. The upper transparent electrode 94 is formed on the upper half mirror 92.
In the MEM unit shown in FIG. 6, a voltage is not applied between the two upper and lower transparent electrodes 94. Therefore, the upper half mirror 92 does not come in close contact with the transparent spacer 93 but is maintained to be formed. As a result, a light 97 emitted from a collimate plane light source 96 provided below the glass substrate 91 is reflected by the lower half mirror 92 and is not transmitted through an MEM unit body.
FIG. 7 is a sectional view showing an internal state obtained in the case in which a voltage is applied between the two upper and lower transparent electrodes in the MEM unit illustrated in FIG. 5.
In the MEM unit shown in FIG. 7, a voltage is applied between the two upper and lower transparent electrodes 94 of the MEM unit shown in FIG. 6. As a result, electrostatic force generated by the applied voltage acts between the transparent electrodes 94 and the upper transparent electrode 94 and the upper half mirror 92 provided thereunder are pushed downward so that the upper half mirror 92 comes in close contact with the transparent spacer 93 to increase the transmittance of a light in an optical path which is orthogonal to the two upper and lower half mirrors 92. Consequently, the light 97 emitted from the collimate plane light source 96 is transmitted through the MEM unit body and is properly scattered by a glass substrate 98 provided above the MEM unit body.
Display devices using the conventional image display unit have problems, respectively.
For example, it is hard to reduce the size of a CRT display device. In a display device having a very small size, there is a problem in that it is difficult to uniformly enhance a lifetime and a reliability and power consumption is also increased.
Moreover, an LCD display device requiring a back light has a problem of the use efficiency of the light. Furthermore, there is a problem in that a TFT (a thin film transistor) requiring a high cost is necessary.
In addition, an LED display device has a problem of the price and lifetime of a light emitting diode, particularly, a blue light emitting diode, and furthermore, a manufacturing cost of a two-dimensional array of the LED.
Moreover, a plasma display device has such an essential problem that a circuit integrating the control system of an image signal and the control system of a power supply required for fluorescent light emission is necessary. For this reason, there is a problem in that the control system of the image signal becomes huge and an operating speed cannot be increased.
Since the MEM unit to be one of the conventional image display units is formed on a glass substrate or a plastic film, there has been a problem in that a special machining technique is to be introduced and the degree of integration cannot be enhanced.
Furthermore, there is a problem in that an image signal is to be converted and processed into a suitable signal configuration for the MEM unit and a semiconductor circuit for driving is to be provided and connected as a separate device from the MEM unit and they cannot be integrated.